Lamp and method of producing a lamp

ABSTRACT

A method of producing a lamp, including: mounting light emitting junctions in respective receptacles; mounting the receptacles on a curved support structure so as to form a three-dimensional array; and placing the light emitting junctions in electrical connection with the support structure.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a lamp usingpre-packaged light emitting semiconductors which are inserted into alead frame and to a lamp produced thereby.

The present invention is an improvement on the subject matter ofInternational patent Publication No. WO 02/103794, the entire disclosureand subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Lighting applications involving the use of light emitting diodes (LEDs)are many and varied. Traditionally, it has been common to use a singleLED as a small and discrete indicator, for example to indicate a statuscondition on a control panel for electrical plant.

It has also been known to provide a number of LEDs arranged in a twodimensional array so as to provide greater light capabilities than wouldbe provided by a single LED. However, not all of these arrangements aresuitable for providing quality domestic or industrial lighting.

It is an object of the invention to provide a lamp, and method ofproducing a lamp, which is an improvement over the prior art or which atleast provides a useful alternative thereto.

SUMMARY

The present invention provides a method of producing a lamp, including:

-   -   mounting light emitting junctions in respective receptacles;    -   mounting the receptacles on a curved support structure so as to        form a three-dimensional array; and    -   placing the light emitting junctions in electrical connection        with the support structure.

The present invention further provides a lamp including:

-   -   a curved electrically conductive support structure;    -   a plurality of receptacles mounted on the support structure so        as to form a three-dimensional array; and    -   a plurality of light emitting junctions disposed in respective        receptacles and electrically connected to the support structure.

The present invention further provides a lead frame for receiving aplurality of light emitting junctions to form a lamp, including:

-   -   a curved, electrically conductive support structure;    -   a plurality of cavities in said support structure for receiving        a respective plurality of receptacles having light emitting        junctions disposed therein, such that said light emitting        junctions form a three-dimensional array.

In accordance with a preferred embodiment of the present invention,there is provided a method of producing a three dimensional array oflight emitting junctions on a supporting structure. This method providesa considerable simplification of the manufacturing process disclosed inprior art, and suggests itself potentially as the likely successor tomethods of mounting light emitting junctions, that are in use today.

Preferably the method provides that light emitting junctions areattached into a one-dimensional or two-dimensional array of preformedmetallic, or other material, electrically conductive cups or otherreceptacles.

Preferably the cups in the linear array, with light emitting junctionsattached, are subsequently singularised.

Preferably the singular cups are unsymmetrical in configuration to allowcorrect orientation, with respect to electrical polarity, of the lightemitting junction within each cup and the orientation of each cup withinthe three dimensional array.

Preferably the singular cups are placed in a series of mating holes to apre-determined pattern, within a curved portion of a lead frame with apart spherical surface.

Preferably the profile of the cups is designed to produce a specificpattern of light from each light emitting junction, such that thecombined light pattern from a three dimensional array of cups on a leadframe is predictable and repeatable in mass production.

Preferably the array of cups so placed in the lead frame are restrainedin their respective holes by welding, soldering, glueing or by othermeans which ensures the continuity of mechanical, thermal and electricalproperties between the lead frame and the cups.

Preferably the cups are installed on electrical conductors within thelead frame which are used to control the flow of electric current andconsequently the luminous output of the light emitting junctions.

Preferably the light emitting junctions are electrically connected totwo conductors within the lead frame by means of intermediateconductors. The arrangement of connections of the intermediateconductors may be configured to allow the light emitting junctions to becontrolled individually or in groups.

In another embodiment the cups in the array, each fitted with a lightemitting junction, are singularised from the array and packaged on tapeand reel, or other commonly used packaging system. Such packagingprovides scope for applications, other than a three dimensional array ona lead frame, where modular mounting of light emitting junctions isdesirable.

In another aspect, there is provided a lamp, formed in accordance withthe above-described method.

In yet another aspect, there is provided a cup for receiving a lightemitting junction, with side walls arranged to direct light which isoutput from the junction, the cup further serving to dissipate heatgenerated from the junction, which is thermally coupled thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described, by way of non-limiting example only, withreference to the accompanying drawings, in which:

FIGS. 1A, 1B and C show plan, cross-sectional side and perspective viewsof a linear array of cups;

FIG. 2A is a cross-sectional side view of a lead frame of convex formillustrating cup insertion;

FIG. 2B is a cross-sectional side view of a lead frame of concave formillustrating cup insertion;

FIGS. 3A and 3B are plan and side cross-sectional views of a lead framefitted with cups and intermediate conductors;.

FIGS. 4A and 4B are plane and side cross-sectional views of an exampleof a cup assembly with a light emitting junction mounted therein;

FIG. 5 is a schematic diagram illustrating electrical connections of alamp of one embodiment of the invention;

FIG. 6 is a process flow diagram of a method of producing a lampaccording to an embodiment of the invention;

FIGS. 7 to 14 illustrate steps in the process of FIG. 6;

FIG. 15 illustrates an alternative form of lamp lead frame (prior tosingulation) according to a further embodiment of the invention;

FIG. 16 illustrates a part of a lamp production process according to oneembodiment; and

FIG. 17 is a plan view of a lamp according to a further embodiment.

DETAILED DESCRIPTION

Like reference indicators are used to indicate like or similar featuresin the drawings.

Referring initially to FIGS. 3A and 3B, preferred embodiments of theinvention relate to a lamp and a method of producing a lamp having aplurality of light emitting junctions 4 mounted on a lead frame 110having curved conductors 10, 11 and 12. The junctions 4 are located inrespective receptacles 2 which are mounted onto the lead frame 110 andsubsequently electrical connections are formed between the junctions 4and the curved conductors, 10, 11, 12 and 13 (being the supplyconductor) to enable an electrical circuit to be completed via each ofthe junctions 4 when the lamp is turned on. Conductors 10, 11 and 12 arethree-dimensionally curved (for example, spherically) but supplyconductor 13 is only two-dimensionally curved (i.e. planar but curved).

The receptacles 2 are formed separately to lead frame 110 and thejunctions 4 are mounted therein prior to the receptacles 2 being mountedon the lead frame 110. The receptacles 2 are preferably formed in bulkfrom a strip or sheet material and then separated from that materialeither before or after the junctions 4 are mounted in the receptacles 2.

A linear array 1 of receptacles 2 (formed preferably as generallyconcave cups), as shown in FIGS. 1A, 1B and 1C, is preferably formedfrom thin sheet metal, copper or the like, by conventional means, suchas pressing or stamping. Other forms of receptacles may be appropriatebut all such receptacles are referred to herein as cups for the sake ofsimplicity. A cup 2 having a junction 4 disposed or affixed therein isreferred to herein as a cup assembly 3, for convenience. Instead of alinear (one-dimensional) array, the cups may be formed in atwo-dimensional sheet array.

One advantageous aspect of the preferred cup is its shape, which allowseach cup to function as an optical guide for controlling the directionof light output from the junction mounted therein. Each cup 2 ispreferably of a generally circular form when seen in plan view, as shownin FIG. 1A, although other forms, such as elliptical or more rectangularforms, may function suitably. The preferred cup form has a circularinner base of radius r, from which cup walls of a generallyfrustoconical shape diverge at an angle X (relative to horizontals asshown in FIG. 1B) toward a lip of the cup, having outer radius R. Thevertical depth from the lip of the cup to the inner circular basesurface of the cup is shown by reference T in FIG. 1B.

As shown in FIG. 2A, the cup assemblies 3 are mounted in the lead frameso that their angular orientation is displaced with respect to oneanother (based on the lead frame 80 having a part spherical shape in thearea where the cups 2 are mounted thereon). This angular displacement isdesignated by reference Z in FIG. 2.

The shape of the cups 2, and dimensions of radii R and r, side(displacement) angle Z and depth T, are preferably determined by theirrespective influence on the light pattern which emerges from the cup. Itis preferred that the luminous intensity emanating from the lamp beoptimised for linearity within the overall angle of incidence, 2 timesangle Y (shown in FIG. 2A), of the beam from the lamp. The solid anglesubtended by the beam, 2×Y is traditionally referred to as the ‘halfangle’. It is defined as ‘the angle within which the luminous intensityexceeds 50% of the maximum value of the beam’. This is a significantfactor in the optical performance of the lamp because it affects theeffectiveness of the illumination provided by a lamp of this nature.

The influence of these factors, R, r, T and angle X, together with theradius of curvature C of the lead frame, and the displacement angle Z,of each cup within the part spherical portion of the lead frame,constitute the parameters which determine the value of angle Y andtherefore the nature of the output illumination pattern of the assembledlamp.

These factors are variables in each lamp design and a variety of lampscan be designed by optimising these variables with respect to thepreferred half angle, the number of cups installed in the lamp, and therelative positions of the cups. For further lamp design examples, pleaserefer to FIGS. 15 and 17.

After formation, the array of cups is preferably plated selectively,with silver, silver alloy or similar material. The plating is to enhancethe optical performance of each cup by providing a highly reflectivesurface, and in addition may simplify the attachment process (eg.soldering or applying silver adhesive) employed to restrain the cups 2in holes 6 (shown in FIG. 2A) in the lead frame.

Subsequent to formation and plating of the linear array of cups, a lightemitting junction (die) 4 is attached to the bottom inner surface ofeach cup to form a cup assembly 3. (Throughout the specification,reference to a “die” is used interchangeably with “junction” and “LED”.)Due precautions are required to align each die consistently with thelinear array. The cups are preferably singularised from the array, byconventional means, and the polarity indicated by notching, stamping (orsome other method) a mark 7 on one side of the cup 2. In one preferredform, the mark 7 is a truncation or flattening of one outer edge of thecup. The formation of the mark 7 on the cups may be performedimmediately after the cups are formed and before plating so as to assistin aligning the junctions consistently with respect to polarity.

In an alternative form of lead frame to the convex domed shape shown inFIG. 2A, a concave form of the lead frame may be formed, such as thatshown in FIG. 2B. Apart from the differences in orientation of curvatureof the lead frame supporting structure, the concave lamp embodimentshown in FIG. 2B may be formed in a similar manner to that of FIG. 2Aand other convex lamp embodiments shown in the drawings and describedherein. In particular, the lamp production process as shown anddescribed in relation to FIG. 6 is applicable to concave lead framearrangements. For example, instead of forming a dome in the centralportion of the lead frame at step 640, a bowl (inverted dome) may beformed. Such a concave form of the lead frame would involve more of afocussing of the light emitted from the junctions and thus such anembodiment would be more suitable for applications requiring a morefocussed, rather than even, distribution of light. This lamp embodimentwould thus have a focal length approximately equal to the radius ofcurvature C of the central curved portion of the lead frame. Theeffectiveness of the focus in this case will be partly determined by themagnitude of the radius of curvature C and will be influenced by thevalues of R r and T.

A lamp is formed by inserting singular cups, complete with dies, intoholes 6 in the curved lead frame conductors 10, 11, 12 of the lead frame110, as shown in FIG. 3A. In the shown embodiment, pairs of intermediateconductors 14, 15, 16 are attached by wire bonding between the activeportion of the dies of a first polarity and conductors 10, 11, 12. Inaddition, pairs of intermediate conductors 17, 18, 19 are attached bywire bonding to the active portion of the dies of a second polarity andto a common supply conductor 13 and conductors 11 and 12, respectively.This configuration allows control of the current, and therefore controlof the intensity of the emitted light, flowing through the groups oflight emitting junctions mounted on conductors 10, 11, 12.

Apart from common supply conductor 13, only three curved lead frameconductors, 10, 11 and 12 are shown in FIG. 3A. It is specificallyenvisioned that a greater number of curved lead frame conductors may beemployed, each supporting a number of cup assemblies. For example, whileFIG. 15 shows an embodiment of the lead frame for supporting 18junctions within respective cup assemblies distributed on three separateconductors 113, 114 and 115, this arrangement may be modified to providefive separate conductors supporting six cup assemblies in each. Furtherembodiments are contemplated, although not shown, in which a largernumber of cup assemblies may be supported, for example in the order of50 to 100.

Although the intermediate conductors 17, 18 and 19 shown in FIG. 3A aredescribed as being in pairs, it may be appropriate to use singleintermediate conductors instead, for example where small, low currentjunctions are employed in the cup assemblies 3.

The embodiment shown in FIGS. 3A and 3B is particularly suitable forlarge junctions which draw greater currents than smaller junctions andthus pairs of intermediate conductors are desirable for allowing foreven collection and supply of current to the active regions of the die.The pairs of conductors also provide a second current path which servesto reduce possible losses associated with having only one intermediateconducting wire to and from the die.

In an alternative embodiment to that shown in FIGS. 3A and 3B, the pairsof intermediate conductors 14, 15 and 16 may be connected to the cupinstead of to curved conductors 10, 11 and 12. In this alternativeembodiment, each of the cups is in electrical connection with the curvedconductors 10, 11 and 12 by virtue of being mounted thereon using aconductive material, such as solder or a silver glue. This alternativearrangement allows for the pairs of intermediate conductors 14, 15 and16 to be attached to an interior wall of the cup 2 prior to mounting ofthe cup in the holes 6 of the curved conductors 10, 11 and 12. In otherrespects, this embodiment is similar to that shown and described abovein relation to FIGS. 3A and 3B.

In a further alternative embodiment (described further below in relationto FIGS. 4A and 4B), instead of the intermediate conductors 14, 15 and16 being connected to the interior wall of the cups, pairs of conductors26 and 27 are connected between the cathode and anode of the die 4 andconductive regions 22 and 23, respectively. Further intermediateconductors are then used to connect between the curved conductors 10, 11and 12 and the conductive regions 22 and 23.

In another embodiment (shown in FIG. 17), the current flowing througheach individual light emitting junction can be controlled independentlyof all others by suitably arranging the connection of intermediateconductors. FIG. 17 shows a possible arrangement of 8 LEDs which can beindividually and independently controlled. In this arrangement, thecentral curved (spherical) part of the lead frame is not partitionedinto separate conductors, but is instead a common conductor 114 for allLEDs mounted on it. It is convenient for consistency to make this commonconductor 114 the cathode (or negative terminal). There are eight anodes132 shown, one for each die, through which the flow of current to eachdie can be controlled. The anodes 132 are arranged in the form of spokesabout the central part of the lamp lead frame. It is convenient to makethe cathode common because AlGalnP dies (Red and Amber) have the cathodeon the underside of the die (which is electrically and physicallyconnected to the cup), so when mounted on a conductor it must be thecathode for these dies, and since InGaN dies (Green and Blue) have aninsulated underside it is convenient to standardize the connections withrespect to polarity. This is the opposite polarity to the lead frameswhich have three groups of LEDs. Common is positive for these becausethe undersides of the chips (negative) may be electrically connected torespective ones of the three curved sections of the lead frame via theconductive cups in which they are disposed.

The light emitted by the LEDs is of a narrow frequency or wavelengthbandwidth, which in the visible spectrum is perceived as a specificcolour. LED's with red, yellow, green and blue light have becomecommonplace. If LEDs of different colours are arranged in a cluster suchas that shown in FIG. 17, it becomes possible to generate light fromLEDs which is perceived to be of a different colour to thecharacteristic colour of any of the constituent LEDs in the array. Bycontrolling the excitation current in each LED, the level of lightoutput may be controlled, which allows the light from the LEDs to becombined in variable proportions thereby generating different colours.

For example, red, green and blue lights can be combined in the correctproportions to give a generally white light appearance. Similarly, thelamp can be arranged to emit light of a single colour by passing currentthrough only those LEDs which have the same wavelength, and to changecolour by reducing the excitation to those LEDs of a first wavelengthand simultaneously increasing the excitation to a group of LEDs of asecond wavelength. A suitable control system can be devised to generateany combination of colour and intensity within the possibilitiespresented by the characteristics of the LED dies installed in the lamp.

Packaging the lamp in selected optically suitable material, such asepoxy resin, can further enhance the process of combining, or otherwise,the light emitted by the LED dies. If, for example, an epoxy or otherencapsulating material is chosen which has low light absorption, minimumback scatter and superior diffusion properties then it may be possibleto achieve an almost homogeneous single colour emission from the lampand to vary the colour widely over the visible spectrum. This may beachieved even though some of the LEDs may be mounted near theextremities of the spherical part of the lamp and have generallydivergent beams of light. In another arrangement, a package of opticallyclear low absorption material may be chosen for a function wherecombination of light into a single colour is of less importance.

The electronics industry has devised many ways of controlling LED arraysand displays. These are generally suitable for small power LEDs—in theorder of 100 milliwatts of power per LED, where the current to becontrolled is in the order of 20-50 milliamps.

LED dies with an area of one square millimeter (die size 1 mm×1 mm)require excitation current to be up to 350-500 milliamps. Developmentsin the industry are expected to deliver LED dies of 2.5 squaremillimeters and larger, which will require excitation currents in excessof 1000 milliamps. In general, LED controllers will be required to havea power handling capacity of 5 Watts per LED, compared to the presentrange at around 100 milliwatts per LED—an increase of 50 times.

The present invention encompasses, but is not restricted to, LED diesizes up to 1.26×1.26 mm which each consume 1 Watt of power. The controlcircuit driving such a lamp must be capable of controlling a number ofsuch LEDs. For example, if 18 LEDs are mounted in the lamp, the controlcircuit will need to be able to drive an output in the order of 18Watts.

In another preferred embodiment, illustrated by FIGS. 4A and 4B,alternative cups 32 are provided with a layer of electrical insulation20, on an upper surface of cup flange 21, with areas of electricallyconductive material 22 & 23 superimposed on the insulation. This allowsthe active areas of the die 24 & 25, to be connected by bonding wires 26& 27, to the conductive areas 22 & 23. These connections can be madeduring the process of attaching the dies to the cups. It presents aconsiderable simplification to the process of wire bonding describedabove, in which the bonding equipment is required to accommodate thelayout of a three dimensional array.

Simple conventional practices can be used to make the equivalent tointermediate connections 14 & 17 shown in FIG. 3A, if the bonding wiresare attached to the cups when they are in a linear array. Thisembodiment further allows the use of packaged light emitting junctionsin many other applications. Commonly used ‘pick and place’ machinery canbe used to automatically install the cups and to make the connections.

Conductive regions 22 and 23 are preferably formed in a thin layer overa layer of insulation applied to the rim of each cup. The insulatingmaterial may be epoxy or some other compound which has good adhesion tothe surface of the cup and gives a good electrical insulation in thinlayer form. The conductive regions may be formed by metal deposition orother suitable process. Such processes are used to produce printedcircuits, in particular metal cored printed circuits which are oftenmanufactured on a metallic substrate of aluminium.

A cup assembly 3 or package (i.e. a cup with a junction mounted on it)has significant advantages over light emitting junctions available inother surface mounting packages. The limitation imposed by poor heatdissipation from conventional packages is largely overcome. A cuppackage can be easily installed directly into a prepared recess in a‘Metal Cored Printed Circuit Board’ (MCPCB), thus having applicationsother than in lamp lighting. An almost ideal thermal path may thus becreated, from the heat source (the die) through the cup material anddirectly into the highly dissipative core of an MCPCB.

Restrictions on the size of a die and the practical limit of power thata die can dissipate control the quantity of light currently availablefrom these devices. By providing a method of effectively andconveniently dissipating heat losses in a die, practical restrictions onthe size of dies which can be employed successfully are effectivelyremoved. Thus, cups designed to accommodate dies which can consumeseveral watts of power, and which produce light somewhat in proportionto the input power, can be produced simply and cheaply.

Examples of large LED dies which can be used in embodiments of theinvention are listed on Table 1 below. For smaller LED dies, there arenumerous varieties on the market and suitable dies would be apparent toskilled persons. TABLE 1 Forward Colour Wavelength Voltage Part NoManufacturer Blue 470 nm 3.6-4.0 V LE470-P2-G AXT Green 525 nm 3.6-4.0LE525-P2-G AXT Amber 590 nm 2.0-2.4 ES-CAYL529 Epistar Red 625 nm2.0-2.4 ES-CAHR529 Epistar

Referring now to FIG. 6, a process flow diagram is shown, by which alamp can be produced according to embodiments of the invention. Thepreferred lamp production process involves forming the cups separately,having junctions mounted therein, and mounting the cup assemblies ontothe lead frame once the lead frame has been manufactured to a certainpoint (i.e. past step 640). Once the cups are attached to the leadframe, they are processed together to form the lamp at step 665.

At step 605, the cups are formed, for example by a pressing tool, from acopper plate or other suitable sheet or strip of deformable conductivematerial, and each of the cups is pressed from the plate or sheet so asto form the receptacles illustrated in FIGS. 1A to 1C. Step 605 includesforming the mark 7 on each cup. Once singulated from the material fromwhich they were pressed, the cups are plated at step 610 with a silver,aluminium or other conductive material, for example by barrel plating,precision plating or vapor deposition, to achieve a plating thickness ofabout 4 to 8 microns. After plating, the dies (referred to as chips inFIG. 6) are attached to the inside base surface of the cup at step 615,preferably by a silver glue so that the junction faces outward away fromthe base surface. Once the junctions are attached at step 615 to thecups, the thus-formed cup assemblies may be packaged into a linear stripor a two-dimensional sheet which can be fed into a robotic pick andplace machine, for example, such as those used in surface mounttechnology.

Independently of cup formation, lead frame processing begins at step 620by machining the basic shape of the lead frame. The machining may be byetching or mechanical stamping and it is preferred that the lead framebe formed of copper or copper alloy sheet material in the order of about400 microns thickness. The thickness of the lead frame material ispreferably chosen for optimum thermal conduction of excess heat awayfrom the cup assemblies. For example, if larger dies are installed inthe cup assemblies there will be more heat generated than if smallerdies are used. Increasing the thickness of the lead frame will assist inconducting this heat away from the lamp. The basic shape of the leadframe formed at step 620 includes conductors 10, 11, 12 and 13 within asurrounding supporting frame of copper sheet material prior to beingspherically deformed and separated into separate conductors. At step625, a center conductive portion (which becomes conductors 10, 11, 12and 13) of each lead frame is plated, preferably with silver oraluminium, to a thickness of about 4 to 8 microns. The plating isapplied at least over the central portion of the lead frame which willreceive the cups and be in electrical contact therewith, but may beapplied over the whole upper surface of the lead frame for economy orconvenience. Once the plating has been completed, holes are punched intothe central (plated) portion of the lead frame, at step 630. These holeswill form the holes 6 shown in FIG. 2 for receiving the cups after thespherical shape has been applied to the central portion of the leadframe. Next, at step 635, the conductors 10, 11 and 12 are partitioned(conductor 13 is preferably already partitioned as part of step 620) soas to separate groups of holes from each other in the central portion ofthe lead frame. This partitioning is preferably performed using a smoothand precise cutting tool so that no additional processing is required tofinish the edges created between the conductors during partitioning.

The partitioning is performed according to the desired grouping of theholes in the central conductive portion of the lead frame. Accordingly,this grouping will depend on the number of holes formed in that portionduring step 630. In a preferred embodiment, nine holes are formed atstep 630. In alternative embodiments, for example such as that shown inFIG. 15, a different number of holes may be formed in the lead frame forreceiving cups with junctions therein. The alternative embodiment shownin FIG. 15 has eighteen holes 120 formed in the central portion of thelead frame 110, with those holes grouped into three separate groups ofsix on conductors 113, 114 and 115. The partitioning step 635 must alsotake account of the deformation of the material of the lead frame duringthe subsequent dome forming step 640. For example, the holes formed inconductor 11 have a tendency to deform (elongate to become somewhatelliptical) slightly along with the deformation of the plated lead framematerial during the spherical dome forming. Accordingly, the holeforming and partitioning steps 630 and 635 may be performed so as tocompensate for deformation of the material during dome forming, forexample by forming the holes on conductor 11 in a flattened ellipticalform so that they stretch out to a more circular form during the domeforming step.

It is preferred that the dome forming step 640 be performed by some kindof press tool so as to provide a generally part-spherical shape to thecentral portion of the lead frame.

At step 645, cup assemblies 3 formed through steps 605 to 615 areattached to the lead frame following the dome forming step 640. Thisattachment is preferably performed by soldering, welding or using aconductive adhesive once the cup assemblies are placed in the holes 6by, for example, precision robotic machinery.

After the cup assemblies are placed into the holes and fixed thereto,wire bonding is performed at step 650 so as to electrically connect thejunctions in the cups to the conductors 10, 11, 12 and 13, as previouslydescribed. For this wire bonding, gold wire is preferably employed usingknown heat/sonic welding techniques, the wire having a diameter in theorder of 25 to 50 microns. Other forms of bonding techniques usingdifferent wire material and wire diameters are common in the industry,and may alternatively be employed.

After the wire bonding, a phosphor is optionally applied over the top ofindividual junctions at step 655. This is done by evenly mixing aphosphor powder into an epoxy and dispensing the epoxy in drops onto thetop light emitting surface of each junction. At step 660, an opticallyclear epoxy resin or thermoplastic is applied to the central part of thelead frame so as to encase it. If no phosphor was deposited over theindividual junctions at step 655, a phosphor powder may be mixed in withthe epoxy encasing the central part of the lead frame at step 660. Inorder to apply the epoxy or thermoplastic, the lead frame is invertedand placed into a mould of a complementary part-spherical shape. Oncethe epoxy resin or thermoplastic has cured or otherwise set, the leadframes are then processed, at step 665, so as to singulate them fromeach other, including punching the conductors 10, 11, 12 and 13 free ofthose parts of the lead frame which held them in place prior to theepoxy application. It is also at this step that webs (evident from thedrawings) connecting the conductors 10, 11 and 12 are removed, forexample by punching, thus electrically isolating those conductors fromeach other.

FIGS. 7 to 14 illustrate the above described process steps and, inconjunction with Table 2 below, serve to illustrate a production processin accordance with a preferred embodiment. Table 2 below summarises someof the processing steps described above and preferred methods andmaterials for these steps. TABLE 2 Material Material Item Process MethodGeneric e.g. Lead Frame Machine Basic a) Etching, or Copper Strip CopperAlloy A194 HH Shape b) Mechanical Nominal Thickness stamping 15 mil.(381Microns) Plating a) Barrel Plating Silver or 4 to 8 Microns b) PrecisionPlating Aluminium c) Vapour Deposition Cup hole Press Tool — formationPartitioning Press Tool — Dome formation Press Tool — Cups Machine BasicPress Tool — Shape Plating Barrel plating Silver or 4 to 8 MicronsPrecision Plating Aluminium Vapour Deposition Cup Attachment Soldering,or Lead/tin alloy or 70/30 Lead/Tin Conductive paste CMI 121-03 GlueingSilver glue Chip Apply adhesive Dispenser Silver Glue CMI 121-03Insertion Chip Placement Robotic LED chip InGaN, AllnGaP Heat TreatmentProcess oven — Wire Electrical Heat/Sonic Welder Gold Wire 25-50 MicronsDiam. Bonding connections Optional Apply Phosphor Dispenser PhosphorHung Ta 80911 465 Powder ˜470 nM, or 11001 471˜474 nM Optically ClearEpifine T-6000A2 & T- Epoxy 6000B Packaging Moulded Epoxy, Mould,Process Optically Clear Epifine T-6000A2 or Oven Epoxy Resin & T-6000Bcatalyst Compression Moulding Machine Optically Clear Degussa Plexiglasdf21 Moulding Thermoplastic 8N Finish Singulation Press Tool —

FIG. 15 shows an alternative form of lead frame 110 having a highernumber of holes 120 disposed in the central portion thereof. Conductors113, 114 and 115 each support six cup assemblies and are arranged so asto generally provide an even distribution of light from the junctionswhen the lamp is in operation. The precise configuration and location ofthe groups of holes on conductors 113, 114 and 115 may be varied asrequired, in order to achieve a desired light output pattern. The numberand positioning of the holes 120 may also be varied, depending onpractical manufacturing requirements.

FIG. 16 illustrates a part of the lamp production process, generallycorresponding to step 645 of FIG. 6, where the cup assemblies are placedinto holes 6 or 120 in the lead frame 110. The lead frames 110 areprocessed across a carrier 119 in sequence so that the cup assemblies 3may be placed in recesses 120 (holes 6). The carrier 119 may beconstructed to mate with the part spherical surface, and the referencemarkers, of the lead frame. This mating part may be either a raisedconvex face which is complimentary to the concave underside of theconvex lead frame, or alternatively be a concave recess which iscomplimentary to the convex underside of the concave lead frame. Convexand concave lamp profiles such as those illustrated by FIG. 2A and FIG.2B may thus be constructed by utilising alternate profiles on thecarrier. The carrier 119 may be rotatable on a shaft 121, for pivotablemovement about an X axis, and a shaft 122, for pivotable movement abouta Y axis. In this way, the lead frame 110 can be positioned at amounting station (not shown) and rotated about the X or Y axis relativeto the mounting station so as to facilitate placement of the cupassemblies 3 in the recesses. Alternatively, if a suitable roboticsmechanism is available, the carrier 119 is fixed in place and therobotic placement machinery can place the cup assemblies 3 into therespective recesses, accounting for the part-spherical shape of thecentral portion of the lead frame. In such an embodiment, referencemarkers are provided along the outer edges on the lead frame 110 forpositional calibration by the robotics machinery.

Certain modifications or enhancements to the embodiments herein beforedescribed will be apparent to those skilled in the art without departingfrom the spirit and scope of the present invention.

1. A method of producing a lamp, including: mounting light emittingjunctions in respective receptacles; mounting the receptacles on acurved support structure so as to form a three-dimensional array; andplacing the light emitting junctions in electrical connection with thesupport structure.
 2. A method as claimed in claim 1, wherein thesupport structure includes a plurality of conductors and the methodfurther includes forming at least one of the conductors in a curvedconfiguration.
 3. A method as claimed in claim 2, wherein at least someof the conductors are formed in a part spherical configuration.
 4. Amethod as claimed in claim 3, wherein the at least some conductors areformed in a convex configuration.
 5. A method as claimed in claim 3,wherein the at least some conductors are formed in a concaveconfiguration.
 6. A method as claimed in claim 2, in which the lightemitting junctions are connected to the at least one curved conductor byintermediate conductors.
 7. A method as claimed in claim 6, wherein eachof the plurality of conductors is curved, one of said curved conductorsbeing two-dimensionally curved and the rest of said curved conductorsbeing three-dimensionally curved.
 8. A method as claimed in claim 7,wherein each junction is electrically connected to two of the curvedconductors.
 9. A method as claimed in claim 2, wherein the junctions areelectrically connected to conductors such that the current flowing ingroups of junctions can be controlled separately to the current flowingin other groups of junctions.
 10. A method as claimed in claim 2,wherein the junctions are connected to conductors such that the currentflowing in any junction can be controlled independently of the currentin every other junction.
 11. A method as claimed in claim 1, wherein thereceptacles are preformed cups.
 12. A method as claimed in claim 11,wherein the cups function as optical guides for controlling thedirection of light output from respective junctions mounted therein. 13.A method as claimed in claim 11, wherein the cups are formed in aone-dimensional or two-dimensional array and are subsequentlysingularised.
 14. A method as claimed in claim 11, wherein the cups aremounted in respective cavities in the support structure.
 15. A method asclaimed in claim 14, wherein the cavities are holes extending throughthe support structure.
 16. A method as claimed in claim 11, wherein thejunctions installed in the cups are electrically connected to conductiveareas, insulated from, but mounted on, a flange of each cup.
 17. Amethod as claimed in claim 13, wherein singularised cups, with lightemitting junctions attached, are packaged in tape and reel, or other,bulk packaging.
 18. A method as claimed in claim 1, wherein the supportstructure is formed as a lead frame.
 19. A method as claimed in claim18, wherein the support structure is formed by: (a) stamping aconductive plate in a predetermined configuration; (b) forming cavitiesin a central portion of the conductive plate for receiving saidreceptacles; and (c) impressing a curved configuration on said centralportion.
 20. A method as claimed in claim 19, wherein said centralportion is separated into separate conductors before the step ofimpressing.
 21. A method as claimed in claim 19, wherein the centralportion is coated with silver or silver alloy.
 22. A lamp formed inaccordance with the method of claim
 1. 23. A lamp including: a curvedelectrically conductive support structure; a plurality of receptaclesmounted on the support structure so as to form a three-dimensionalarray; and a plurality of light emitting junctions disposed inrespective receptacles and electrically connected to the supportstructure.
 24. A lamp as claimed in claim 23, wherein each receptacle isa cup.
 25. A lamp as claimed in claim 24, wherein each cup has sidewalls arranged to direct light which is output from the junction, thecup further serving to dissipate heat generated from the junction, whichis thermally coupled thereto.
 26. A lamp as claimed in claim 24, whereineach cup further includes an electrically insulative layer, upon whichis provided an electrically conductive area, to allow for electricalconnection between a bonding wire of the light emitting junction mountedin the cup and an intermediate connection for coupling the junction to aconductor, for establishing a current through the light emittingjunction.
 27. A lamp as claimed in claim 24, wherein each cup is formedwith a polarity indicator toward one side thereof for indicating thepolarity of the junction disposed therein.
 28. A lamp as claimed inclaim 23, wherein the support structure includes a plurality ofconductors, at least one conductor being curved, and the receptacles aremounted on the at least one curved conductor so that the light emittingjunctions adopt a three-dimensional array.
 29. A lamp as claimed inclaim 22, wherein one or more of the junctions is adapted to emit lightof a different color to the other junctions.
 30. A lamp as claimed inclaim 28, wherein the light emitting junctions are connected to the atleast one curved conductor by intermediate conductors.
 31. A lamp asclaimed in claim 30, wherein each of the plurality of conductors iscurved, one of said curved conductors being two-dimensionally curved andthe rest of said curved conductors being three-dimensionally curved. 32.A lamp as claimed in claim 31, wherein each junction is electricallyconnected to two of the curved conductors.
 33. A lamp as claimed inclaim 23, wherein the junctions are electrically connected to conductorssuch that the current flowing in groups of junctions can be controlledseparately to the current flowing in other groups of junctions.
 34. Alamp as claimed in claim 23, wherein the junctions are connected toconductors such that the current flowing in any junction can becontrolled independently of the current in every other junction.
 35. Alamp as claimed in claim 24, wherein the cups are mounted in respectivecavities in the support structure.
 36. A lamp as claimed in claim 35,wherein the cavities are holes extending through the support structure.37. A lamp as claimed in claim 28, wherein at least some of theconductors are formed in a part spherical configuration.
 38. A lamp asclaimed in claim 37, wherein at least some of the conductors are formedin a convex configuration.
 39. A lamp as claimed in claim 37, wherein atleast some of the conductors are formed in a concave configuration. 40.A lamp as claimed in claim 23, wherein the support structure is formedas a lead frame.
 41. A lamp as claimed in claim 40, wherein the leadframe is formed of copper or copper alloy.
 42. A lamp as claimed inclaim 41, wherein at least a part of the lead frame is coated withsilver or silver alloy.
 43. A lamp as claimed in claim 23, wherein thereceptacles are formed of copper or copper alloy.
 44. A lamp as claimedin claim 43, wherein the receptacles are coated with silver or silveralloy.
 45. A lamp as claimed in claim 40, wherein the support structureis formed by: (a) stamping a conductive plate in a predeterminedconfiguration; (b) coating a central portion of the conductive platewith silver or silver alloy; (c) forming cavities in said centralportion for receiving said receptacles; and (d) impressing a curvedconfiguration on said central portion.
 46. A lamp as claimed in claim45, wherein said central portion is separated into separate conductorsbefore the step of impressing.
 47. A lead frame for receiving aplurality of light emitting junctions to form a lamp, including: acurved, electrically conductive support structure; a plurality ofcavities in said support structure for receiving a respective pluralityof receptacles having light emitting junctions disposed therein, suchthat said light emitting junctions form a three-dimensional array.
 48. Alead frame as claimed in claim 47, wherein the support structure isformed by: (a) stamping a conductive plate in a predeterminedconfiguration; (b) forming cavities in a central portion of theconductive plate for receiving said receptacles; and (c) impressing acurved configuration on said central portion.
 49. A lead frame asclaimed in claim 48, wherein said central portion is separated intoseparate conductors before the step of impressing.
 50. A lead frame asclaimed in claim 48, wherein the central portion is coated with silveror silver alloy.